This invention pertains to a purged gate valve suitable for controlling the flow of particulate solids. It pertains more particularly to a gate valve assembly having multiple gas purge passages associated with the seat and gate for preventing deposits of particulate solids and facilitating their flow through the valve.
There is a growing need in industry for handling powdered materials, such as powdered coal feed to steam boilers or coal and lime to coal gasifiers, and for suitable valve devices for reliably controlling the flow of such solids even when the solids are at high temperature. Because the pressure of such fine solids usually exceeds atmospheric, the finely divided material usually causes problems of clogging or even plugging valve flow passages and thus interfering with reliable valve operation. Several valve designs have been developed for handling such particulate solids, for example, as disclosed in U.S. Pat. No. 3,006,357 to Woerner; U.S. Pat. No. 3,547,140 to Hastings et al.; U.S. Pat. No. 3,918,471 to Bedner; and U.S. Pat. No. 4,070,161 to Harter. Although considerable efforts have been made to solve these problems in handling particulate solids using valves of various designs, none of the known prior art designs have been found to be entirely satisfactory for handling the flow of such fine particulate solids.